They programmed the robot arm to move towards a point in mid-air already occupied by a volunteer's outstretched forearm, so the robot would push the human out of the way. Each volunteer was struck 18 times at different impact energies, with the robot arm fitted with one of two tools - one blunt and round, and one sharper.

The volunteers were then asked to judge, for each tool type, whether the collision was painless, or engendered mild, moderate, horrible or unbearable pain.

This is all very good, in the pursuit of creating still more ways for people to fear technology. However, the Ljubljana team needs to catch up to the stabbing robot experiment.

Elizabeth Letourneau, an associate professor at the Medical University of South Carolina, studied crime statistics from 30 states and found, "There is zero evidence to support the idea that Halloween is a dangerous date for children in terms of child molestation."

In fact, she says, "We almost called this paper, 'Halloween: The Safest Day of the Year,' because it was just so incredibly rare to see anything happen on that day."